Mother Knows Best
by Katlover98
Summary: Alpha Mary decides it's time to claim an Omega and sets her eyes towards her youngest. SPNKINK MEME FILL TW: mother/son incest, Mary/Sam Winchester, ABO more inside


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 **In Hunter society, Omega's must-have ritualized, coming-of-age sex with their Alpha parent to be considered adults, and are expected to have had kids if they decide to Hunt full-time. The Winchesters were given some leeway, with Mary dead and John and Dean Betas.**

 **But now Mary's back and when she finds out Sam's an Omega, she decides to take care of both issues.**

 **A/b/o, culturally ok incest, knotting, breeding, dub/non-con, mpreg, dirty praise kink, claiming, marking**

 **First time writing Mary/Sam so I hope you like. All mistakes are my own; enjoy.**

Mary stared at her youngest son as he tried to find a hunt. Sam was a smart boy with good instincts for hunting. He was a valuable asset for not only the Winchester family but for the whole hunting community. Unfortunately, there was a problem. Sam was an Omega and he had yet to be claimed and have pups so he could continue hunting.

Mary came from an old bloodline of hunters and they have traditions that they have kept. Oh, they can adapt to modern times, they were hunters after all and hunters needed to be flexible, but they had kept one tradition. A tradition that ensured the next generation of hunters was born. Any Omega who wanted to continue actively hunting and be considered an adult must have been knotted with an Alpha member of his or her pack and give birth at least once. Sam had yet to do either.

Mary understood after all both Dean and John were Beta meaning there were no Alpha members to knot with Sam but she also knew that they could've asked any Alpha Hunter to have knotted Sam. Apparently, they had failed to do so but now Mary was back and she was an Alpha which meant that she could remedy the situation. Unfortunately, Mary had to do it when Dean wasn't around as he was very protective of Sam.

As a matter of fact, when she had brought it up to Dean he had quickly shut her down and refused to talk about it. She knew she couldn't let Dean know what she was thinking or he would take Sammy as far away from her as possible which only led her to one course of action; talking to Sam.

The ideal time came when Dean had to go to pick up a spare part he needed for the Impala. He would be gone for three days which was more than enough time for Mary to knot and also mate and claim Sammy. She was Alpha enough to admit that her youngest did things to her and Sammy was too old to be without a proper mate.

Did she feel bad for doing it behind Dean's back, yes, but Sammy was an Omega and he had no mate or pups. He had hunting but that wasn't enough for an Omega. Besides, what if Sam died, he wouldn't leave any pups to carry on the Campbell and Winchester's bloodline. No, this needed to happen.

"Alright Sammy, mom; I'll be gone for just a few days, I'll call if anything happens. Are you sure neither one of you want to come with me?"

"Nah, I just found a new book I want to start on. It's on the history of blood magic."

"Nerd," Dean teased fondly "how about you mom, Sam isn't going to be much company."

Mary smiled, "It's okay Dean, I want to get to know Sam better."

Sam gave her a sweet smile that she couldn't help but recuperate."

"Alright, bye mom, I love you. Sam, if anything happens, call me."

"Yes, _mom._ "

Dean rolled his eyes and left with one last glance at them both. Mary started with her plan.

She let Sam read his book for a few hours before she started. First, she went to Sam's room and made a little nest of her and Sam's clothing, blankets, pillows, and towels. It was important for an Omega to have a little love nest before he or she was mated. Besides, Sammy was her youngest son and she wanted him as comfortable as possible.

Then she brought Sam snacks, drinks or anything else he might need and purposely rubbed against him so he could get used to her smell. Finally, when Sam put the book down Mary implemented the last part of her plan, seducing Sammy.

"So, Sammy," she couldn't help but tuck a lock of hair behind his ear, "Have you ever thought about mating, starting a family, caring for pups and watching them grow?"

Mary saw Sam blush and she couldn't help but imagine how beautiful that flush would be if it was with arousal.

"Uh, not really, there just never seemed to be a good time for stuff like that, you know?"

"Hmm, don't you think it's time, though?"

Sam swallowed as she gently ran a finger down his cheek, "What—what do you mean?"

"I mean, is hunting enough, Sammy? Omegas usually need more stability and family. I don't think hunting might be enough, do you?"

"I don't just have hunting, I have Dean, too."

"Hmm, I'm not saying that Dean isn't there, I'm just saying that as an Omega, you can't tell me you've never thought of being mated," she got up and straddled her youngest's thighs, "of having pups, of watching them grow," she whispered the last part, "of having someone there taking care of you during your heats."

Sam swallowed, he _had_ thought of it and it was always followed by guilt. How could he possibly think like that when there were people out there dying? Besides, whenever he had tried for normal it had always blown up in his face. So no, he didn't think about it consciously but sometimes his mind would betray him and he would picture himself with a strong Alpha taking care of him while he watched over his pups running around with another pup in his womb…Sam shook his head.

"Huntings enough," he insisted.

Mary sighed. She knew her youngest was stubborn, a trait he had gotten from his father, and the Campbell's if she was being honest.

"Sammy, I'm an Alpha and even I feel hunting isn't enough. I can't imagine how you're feeling, baby."

"What Alpha would even want me, mom? I'm tainted, I'm tall, I'm ugly, I'm not—I'm not Omega enough."

Mary was saddened by Sam's admission. Her son was _beautiful_ and any Alpha would be so lucky to have him. Of course, she was the one who was going to mate her youngest. Who else could take better care of him than his own mother?

She took Sam's face between her hands and kissed him gently on his lips, "My baby boy, my little Omega, you are so beautiful and, if you would have me, I would be more than happy to mate you, breed you, and take care of you and our pups for the rest of our lives."

Sam couldn't believe what he was hearing. He knew that the Hunter community had rules that involved Omegas and their Alpha family members but Sam had never had to worry about that. Now that his mom was back it seemed she wanted to fill that role.

"But, but it would be wrong," he tried to argue, "Dean says—he says," Sam was interrupted by his mom.

"Dean doesn't understand, neither did John, they are Beta they don't understand the underlying needs both Alphas and Omegas have. Sammy, my Sam, please, you have to accept."

"I don't know—I mean, how would this even work," he asked shyly, "Dean would have an aneurysm if we did and he would be furious."

"Baby, I will deal with your brother, after all, an Alpha's job is to protect her Omega mate from any danger now, isn't it? Besides I'm his mother, I'm _your_ mother, which means he has to back off."

Mary could tell that while Sam liked the idea he was still struggling with accepting it so she got up, pulled Sam's hand and had him standing before guiding him to his, hopefully soon it will be _their,_ room and helping him sit down on the bed, on top of the nest she had made especially for this moment. She started unbuttoning Sam's shirt slowly, relishing the moment.

"But, mom, I," Mary kissed her youngest, exploring his lips, urging him to open up to her so she could explore his deliciously hot mouth. Damn, she and John made beautiful boys. Sam didn't open up but he didn't stop her either which was good enough for Mary. She finished unbuttoning his shirt and then helped him out of it. She frowned when she saw the t-shirt underneath. Why did Sam insist on wearing so much clothing? She would have to change that later on but right now she took off his shirt and then had him lie down.

Sam stared up at her wide-eyed and shyly. To make Sam feel better and less vulnerable she took off her own shirt, slowly, relishing Sam's expressions as she teased him. As soon as she took off her shirt it was immediately followed by her bra. She was in front of her future mate, braless and proud. She straightened out her back so her breasts would stand erect and firm. She couldn't help but smile at Sam's obvious lust. His pupils were so big that she couldn't see any hazel

"Like what you see, baby boy? You know you nursed from these tits, I helped you grow with the milk I fed you just like you will nurse any pups I give you from your breast."

Mary smelled the sharp scent of Sam's arousal as she said those words, "You like that baby boy?"

Sam nodded, all doubts blown away from his mind as his arousal took over. He should be embarrassed at how much slick he was producing, especially since he wasn't in heat but he couldn't help but be turned on by this strong, confident, Alpha, something he never thought he would see be directed at him.

Mary climbed on top of Sam's thigh and kissed him fiercely, this time he let her take over and she was able to ravish his mouth. She felt as Sam starting playing with her breasts until her nipples were erect and her chest felt heavy. She could feel her clit unfurling so that her knot could enter Sam.

She broke off the kiss and smiled when Sam whined, "Don't worry, I just want to finish undressing you."

Mary took Sam's jeans off slowly. As skin was shown she kissed and mouthed at it. Her mouth watered as she took in the full scent of Sam's Omega perfume. He smelled of roses and had a faint smell of books. Mary had no idea why the smell of books was turning her on but they were. She finished taking off Sam's jeans and kissed her way up his leg until she mouthed Sam's hard one.

"Oh, fuck," Mary couldn't help but smile.

"Like that, baby," she got up and took off Sam's boxers quickly. Sam's cock sprang free, already at full attention. Mary couldn't help but put her mouth on the mushroom head. Sam bucked in her mouth and she had to hold down Sam's slim hips. If she wasn't an Alpha she doubted she would have been able to do so.

Mary went back to Sam's cock and licked and sucked all the way down. She took his balls in her mouth while she played with his leaking hole. She didn't put any fingers in, she only kept them over his hole and liked how much slick he was producing. She got up and made sure Sam was watching her as she licked his slick clean from her fingers.

Sam whined and presented himself by going on his stomach and pushing his beautiful ass up, "Alpha, please, need you now, I feel so empty."

Mary had to concentrate so that she didn't cum in her pants. Keeping her knot down while Sam was looking up at her with smokey eyes that spoke of arousal, pink cheeks, and his hole winking at her was the toughest thing she could have ever done.

"Oh baby, you are so beautiful," she took off her pants and panties all at once and watched as her youngest hip's started swaying back and forth. She was going to go slowly, play with him, touch his body, eat him out, and a bunch of other stuff but at the moment she didn't think either of them would last.

So she got behind him on her knees and still opened Sam up a little with her fingers; his hole was already opened but she didn't want to hurt him, who knew how long it was since he last had sex with an Alpha.

Mary used first one, then two, and finally ended up with four fingers up Sam's hole while she stretched it.

"Mom, please, Alpha, I'm ready, want you _inside_ me, now!"

Mary couldn't help but smile, "how can I ever deny you, baby?"

She blanketed Sam's back with her body and kissed his neck before she slowly started feeding her length into Sam's willing body. Sam felt proud when Sam gave a loud, drawn-out moan and bucked against her to make her length go deeper in. Fuck, Sammy's hole was like a vice. It was tight and hot and she couldn't say that she didn't miss having a willing Omega under her. Being with John was good, magnificent, but she did miss being in an Omega's ply body.

Sam mewled in pleasure but there was something else in the sound that had her stopping. There was pain tinged in it.

Sam turned to look at her, "Why'd you stop Alpha? Am I—Am I not good enough," he asked shyly.

Something occurred to Mary at that moment, but it was so ridiculous that she couldn't believe it to be true. So instead she asked something else, "Sammy when was the last time you had sex with an Alpha?"

Sam blushed. No, it couldn't be, Sam was thirty-four years old, it couldn't be that he was, "Sammy, are you a virgin?"

Sam jutted out his chin in defiance, "I've had sex before, mom."

"That's not what I meant and you know it, young man."

Sam shrugged as best he could with his shoulders on the bed, "I'm having sex with an Alpha now."

Mary had to smile a bit, Sam was a sassy boy. Then what he said really hit her, "You're a virgin, I'm the first Alpha to be in your body."

Sam buried his face into the pillows; Mary wasn't having any of that, "I love you so much. Thank you for giving me this gift. When an Omega decides to lose their virginity that Alpha is proud and grateful at the same time."

Sam looked at her and gave a small smile, "I think I'm ready now, Alpha."

Mary smiled, "I wish you had told me beforehand, I would've gone slower."

"Too embarrassing," he answered.

Mary kissed his neck and went back to slowly pulling in and out of her youngest; she was being more careful this time.

Soon, though, Sam started whining, "Faster, Alpha, I wanna really feel it."

Mary growled and really started pistoning in and out of Sam, "Is this what you want my filthy little Omega?"

"Yes," he whined out, "Faster."

"You're such a slut for my knot aren't you, baby? But only my knot, this the only knot that will ever be in you, the only knot that will breed you."

Sam bared his neck to Mary and the next words had her knot inflating in the warm body that was Sam, her baby boy, "Claim me, Alpha, please."

Just as she tied them together she bit Sam's neck, deep, and then he came. Mary felt like she was floating in the clouds. She had done, she had mated Sam. After a few seconds to catch her breath she rearranged them so that they were on their side. They were going to be tied a while, her knot always taking close to an hour to deflate.

They were both breathing heavily and she could tell that Sam was tired, his eyes barely open. She was kind of proud she could fuck her mate silly. She kissed the side of his neck, where she had left her mark and then started licking away the blood.

"Go to sleep, Sammy, I'll be here to take care of you," as she spoke she pulled clothes from their nest closer to Sam so he could smell their combined scent.

"When you wake up again, I'll show you how much fun it could be to get eaten out."

"'Kay, mommy."

Mary smiled, glad that this beautiful Omega had accepted her as his Alpha.

OoOoOoOo

On their second day of doing nothing but love making Sam's scent had shifted. She knew she had gotten him pregnant. Though a part of her was happy she hoped it wouldn't freak Sam out. It hadn't.

"This is awesome, I never thought I would have—well, that is, I went to a doctor a few years ago and he said the chances of me conceiving was low because my abdomen was so scarred. Had given up having pups a while ago."

Sam played with a loose string from one of Mary's blouses. She was behind him, spooning him and took him deeper into her arm, wanting to, no needing to, provide her mate, her youngest child comfort.

"It's okay, baby, I'm here."

OoOoOoOo

Dean entered the Bunker three days later and immediately felt something was off. He sniffed the air trying to catch if there was any danger. It was true that being Beta his sense of smell wasn't as good as an Omega's or Alpha's but he knew the smell of sex when it was in the air. He also knew Sam's and his mom's scents and those two scents were mingling together in the air.

"She didn't," he whispered before what he was smelling truly hit him, "They didn't! Mom, Sammy, where the hell are you?"

Mary was admiring her new mate, looking at his beautiful body and feeling the texture of his soft skin when she was taken out of her reverie when she heard her eldest screaming through the bunker.

"Mom, Sam, you'd better answer me, now!"

Mary sighed. She knew this was coming but she had hoped she would have more time. She kissed Sam's cheek, settled him down after stirring a little bit, put on her robe, and went outside to meet her eldest son.

Dean was furious as he saw his mom leaving Sam's room in nothing but a robe. He could tell there wasn't anything underneath it.

"What the fuck did you do?"

"Keep your voice down, Dean. Sammy's sleeping, let's go talk in the main room."

Dean wanted to argue but he also didn't want to wake up Sam and scare him so he followed his mother; the mother he had trusted with Sammy. The mother that had betrayed his trust and had fucked and claimed his younger brother. His vulnerable, younger, Omega brother.

"Explain yourself, now."

Mary had the audacity to sigh, sounding put out. Dean had to grind his teeth to stop from saying something stupid.

"Dean, Sam is, was an unmated Omega. He was scared and vulnerable; he needed an Alpha."

Dean swiped the table clean of everything that was on it, including a lamp. It was only the years that she had hunted that kept her from flinching. Dean's expression almost had her doing so, though. Her eldest was terrifying.

"All _I'm_ hearing is that you took advantage of a lonely, vulnerable Omega and had your way with _my_ baby brother!"

"Dean, Sam consented."

Dean snorted, "Why do I find that hard to believe."

Mary was starting to have an idea that had her almost growling, "Dean, you don't have _feelings_ for Sam, do you?"

"What," he asked with incredulity in his voice, "of course not, what kind of sick fucker do you think I am? He's my little brother. Speaking of, he's _your_ son. How could you do that with your kid?"

Mary sighed. It was so hard for Betas to understand what an Alpha and Omega felt.

"Dean, Alphas, and Omegas end up mating all the time even if they're related. It doesn't affect us the same way it does Betas and I suspect you know this already."

Dean sat on a chair and put his hands on his face, "God, dad and I we tried so hard to make sure Alphas didn't sniff Sam around and drove them off."

"Dean, I'll take care of Sam, I promise. After all, he is still my son."

Dean gave a humorless laugh, "Like that stopped you. You know what gets me, that you knew exactly how I would react and that's why you waited until after I left."

"Dean, I'm sorry, but you're so protective. A little too overprotective. I know you boys have only had each other but I'm here now. Had you been Omega I would've mated you, too. Dean, Sam and I, we need this, please understand."

Dean growled a little and he looked up at her, seemingly getting ready to attack. She could definitely believe that Dean would be able to drive Alphas off that were sniffing around Sam but he didn't understand that in the long run, it just hurt Sammy. She remembered with sadness how he thought he was unwantable, unloveable because no Alpha had ever set their eyes on him. Apparently, they had but Dean and John had been too overprotective.

"Dean," both of them turned as the soft voice, "Dean, I wanted this."

"Sammy."

"No Dean, I've wanted an Alpha for a long time but I thought, well, I thought I just wasn't good enough for them. But now I have mom, she's a good Alpha, I promise."

Dean deflated with every word that Sam said. Finally, he sighed, "I won't pretend that I understand, but if your happy, I guess I am, too. Just please keep the PDA away from me."

Sammy smiled, "Deal."

Dean sighed one more time and got up to get a drink, "By the way, you're about to be an uncle."

"Seriously, already?"

Mary couldn't help but smile.


End file.
